This invention generally relates to dishwashers. More particularly, this invention relates to a rotatable spray arm for a dishwasher.
Dishwashers typically have a rotatable spray arm for dispensing jets of water. The jets of water are directed to spray dishes that can be loaded onto racks in the dishwasher. Typically, at least some of the jets of water are dispensed from nozzles in the spray arm which are angled so that the thrust from the jets causes the arm to rotate. Some dishwashers have both upper and lower spray arms. However, the present invention relates primarily to a lower spray arm.
A dishwasher generally has an enclosure which forms a basin at the bottom. The lower spray arm is elevated to rotate in a horizontal plane above the basin.
There are normally two racks for holding dishes. A lower rack is typically positioned just above the lower spray arm, and an upper rack is typically positioned near the top of the enclosure. If the dishwasher has an upper spray arm, the upper arm can be rotatably mounted usually below the upper rack.
The water jets wash food particles from dishes on the racks. The water and food particles then collect in the basin at the bottom of the dishwasher. Water in the basin is recirculated for washing. The water in the basin, which can contain food particles, is drained from the basin into a pump. The pump directs the water under pressure back to the spray arm nozzles.
A typical lower spray arm is rotatably mounted on a hub. The arm is typically a single, hollow component having two symmetrical members. Central to the symmetrical members is a flanged portion for mounting the arm on the hub. The hub is typically a cylindrical member which extends upwardly from the bottom of the dishwasher. The flanges are circular and shaped to fit around the hub. The hub generally has at least one port for delivering the water from the pump into the arm. The water then travels through the arm from which it exits through several nozzles.
A small gap is usually provided between each flange and the hub. The gap between each flange and the hub allows a film of water to flow between the two components. This film of water reduces friction between the flange and the hub as the arm rotates.
The water flow through the gap is desirably small so that the flange acts as a sort of seal, causing the majority of water delivered from the ports in the hub to escape through the nozzles in the spray arm. Unfortunately, food particles carried by the water can become lodged between the flange and the hub. Such lodged particles can impede the rotation of the spray arm around the hub.
A traditional flange on a dishwasher spray arm is of uniform annular shape, i.e., it has a uniform contour around the hub. Therefore, if a particle of food becomes interposed between the flange and the hub of a traditional dishwasher, the food particle could roll between the flange and the hub indefinitely as the spray arm spins.
U.S. Pat. No. 3,009,470 discloses a dishwasher having a horizontal, circular spray arm seal which has a beveled edge. A socket and pivot arrangement maintain a plane of rotation of the spray arm so that a gap is always open at the seal. An expandable coupling on the spray arm provides flow to an upper spray arm.
U.S. Pat. No. 5,131,420 discloses a dishwasher having a rotatably mounted spray arm. A pump is provided which has a centrifugal impeller and drain pump impeller mounted on a common shaft.
A need, therefore, exists for a spray arm flange that can act as a bearing and a seal, having a self-cleaning action.